Method and apparatus for testing solderability of electrical components

ABSTRACT

The described embodiments relate generally to methods and apparatus for use in determining solderability of an electrical component. One particular aspect relates to apparatus comprising a vacuum chamber, a load sensor, a platform and a control module. The load sensor has a contact portion disposed within the vacuum chamber and the platform is disposed in relation to the contact portion and has a component mounting surface and a mounting member for mounting an electrical component to the component mounting surface. The control module causes relative movement between the platform and the load sensor so that a contact surface of the electrical component is brought into close proximity with the contact portion. When the contact portion has solder thereon and the solder is brought into contact with the contact surface, the load sensor measures force arising from wetting of the solder to the contact surface. The force generated under contact changes over time, depending on the degree of solderability of the electrical component. Thus, measurement of the wetting forces over time provides an indication of the solderability of the electrical component.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 11/400,233,filed on Apr. 10, 2006, entitled METHOD AND APPARATUS FOR TESTINGSOLDERABILITY OF ELECTRICAL COMPONENTS, the entire contents of which areherein incorporated by reference.

TECHNICAL FIELD

The embodiments described herein relate generally to methods andapparatuses for testing the solderability of electrical components, suchas surface mount components. In particular, the testing involvesautomated measurement of surface tension in the solder when contactedwith a surface of the component.

BACKGROUND

Many small electronic components are mounted on Printed Circuit Boards(PCB) using surface mount technology (SMT). These SMT components areplaced on the appropriate location on the PCB and are subsequentlysoldered to the PCB by known processes. In order to determine thelikelihood of failure of the solder connection between the SMT componentand the PCB, it is necessary to perform testing of the solderability ofsamples of the component.

Current instruments being used for solderability testing essentiallyinclude analytical balances with a built-in clock poised over moltensolder. The SMT component is suspended from the bottom of the balanceprior to testing. The SMT component has flux applied to it and is dippedinto the molten solder. The solder may be in a bath or formed as a smallglobule. The resulting surface tension of the molten solder wetting tothe component is measured by the analytical balance over a period oftime. The resulting measurements are used to plot a graph of the wettingforce (i.e. the surface tension) versus time, which is then used todetermine whether the component has suitable wetting properties forproviding good solderability. In order for the quality of solderabilityof the component to be considered adequate, the sample component mustwet quickly enough during the time that it is in contact with the moltensolder and must exhibit a wetting force large enough to provide asuitably sized solder fillet in the completed solder joint.

Where the testing uses small solder globules, and as availablesolderability testing instrument pin sizes have decreased from a 4 mmdiameter to 1 mm, the limitations of the testing arrangements describedabove make it difficult to accurately measure the wetting forces of thenewest small components. This is in part because of the smaller amountsof solder required for the smaller pins. The sensitivity of theequipment used to measure the wetting forces in such arrangements isinadequate for the smaller wetting forces required to be measured forthe smaller SMT pin sizes. Some such arrangements have a smallest fullscale division of force measurement in milliNewtons, which is inadequateto measure forces in the order of microNewtons. The newly developedsmall pin sizes and smaller solder amounts required for such pin sizesmeans that greater precision in force measurement is needed. However,when measuring such small forces, thermal currents in air at standardpressure may be high enough relative to the small wetting forces thatunreliable results would be recorded or the test may be compromised.

Further, arrangements that rely on suspending a sample over moltensolder before contacting the solder suffer from non-uniform heating ofthe component sample. As the heating in a real reflow oven in the normalassembly process is relatively uniform, it is desirable to mimic suchconditions during the testing process, if possible. While the abovedescribed arrangements can suspend the component sample over the moltensolder for a period of time to heat it prior to immersion in the solder,this generally does not result in uniform heating of the componentsample.

It is desired to address or ameliorate one or more shortcomings ordisadvantages of prior methods and systems for testing the solderabilityof surface mount components, or to at least provide a useful alternativethereto.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described in further detail below, by way of exampleonly, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic front view of a solderability testing apparatusaccording to one embodiment;

FIG. 2 is a block diagram of a system for testing solderability,including the apparatus of FIG. 1; and

FIG. 3 is a flow diagram of a method of measuring the solderability ofelectrical components.

DETAILED DESCRIPTION

Embodiments described herein relate generally to methods and apparatusfor use in determining solderability of an electrical component. Oneparticular aspect relates to apparatus comprising a vacuum chamber, aload sensor, a platform and a control module. The load sensor has acontact portion disposed within the vacuum chamber. The platform isdisposed within the vacuum chamber in relation to the contact portionand has a component mounting surface and a mounting member for mountingan electrical component to the component mounting surface. The controlmodule causes relative movement between the platform and the load sensorso that a contact surface of the electrical component is brought intoclose proximity with the contact portion. When the contact portion hassolder thereon and the solder is brought into contact with the contactsurface, the load sensor measures force arising from wetting of thesolder to the contact surface. The force occurring under contact changesover time, depending on the degree of solderability of the electricalcomponent. Thus, measurement of the wetting forces over time provides anindication of the solderability of the electrical component.

Providing a vacuum chamber in which the solderability testing can becarried out allows for minimization of thermal currents that might causespurious results in the surface tension measurements. In one embodiment,a load sensor having a measurement accuracy similar to that of an atomicforce microscope may be used. Such precision allows measurement offorces in the order of microNewtons.

In one embodiment, the apparatus comprises a first receptacle containingsolder, the first receptacle being positioned on the platform. A firstheating element is associated with the first receptacle for heating thesolder in the first receptacle. A first temperature sensor is alsoprovided for sensing a temperature of the solder in the firstreceptacle.

In another embodiment, the apparatus further comprises a secondreceptacle containing flux, the second receptacle being positioned onthe platform. The first and second receptacles have, in one embodiment,closable openings arranged to be closed when the contact portion is notbeing dipped into the respective first or second receptacle. In anotherembodiment, a second heating element is disposed on the platform. Thesecond heating element has an upper surface comprising the componentmounting surface. The mounting member is disposed on or adjacent thecomponent mounting surface. A second temperature sensor is provided forsensing a temperature of the second heating element.

In one embodiment, the load sensor comprises a projection and thecontact portion is disposed at a tip of the projection. The load sensorfurther comprises a third heating element disposed adjacent the contactportion. A cooling element may also be disposed around the projectiondistally of the contact portion. The projection comprises a downwardlypending pin of relatively small diameter, for example in the order of0.5 mm or less. The platform is disposed below the contact portion ofthe projection. The contact portion is formed of a material that iselectrically and thermally minimally—or non-conductive.

Another particular aspect relates to a method for measuringsolderability of an electrical component. The method comprises the stepsof: mounting at least one electrical component to a component mountingsurface within a vacuum chamber; applying flux to a contact portion of aload sensor, the contact portion being disposed within the vacuumchamber; creating a vacuum in the vacuum chamber; applying solder to thecontact portion; causing relative movement between the at least oneelectrical component and the contact portion so that a respectiveelectrical component is brought into close proximity with the contactportion and the solder contacts a contact surface of the electricalcomponent; and measuring by the load sensor force arising from wettingof the solder during contact with the contact surface.

The method may be used to measure the solderability of more than oneelectrical component and/or more than one surface of a component, inwhich case the steps of applying flux, applying solder, causing relativemovement and measuring the surface tension are repeated for eachelectrical component and/or surface.

The at least one electrical component is disposed below the contactportion. Further, the step of causing relative movement comprises movingthe at least one electrical component relative to the contact surfacewhile the contact surface is held stationary. The step of applying fluxcomprises moving a flux container containing flux relative to thecontact portion to dip the contact portion into the flux container. Thestep of applying solder comprises moving a solder container containingsolder relative to the contact portion to dip the contact portion intothe solder container. In order to achieve the relative movement of theelectrical component, the flux container and the solder container, eachis mounted to a moveable platform within the vacuum chamber or a membersupported by the platform.

Another particular aspect relates to a system for measuringsolderability of an electrical component. The system comprises a vacuumchamber, a load sensor, a support, a control module, a computerprocessor and a memory. The load sensor has a contact portion which isdisposed within the vacuum chamber. The support is disposed within thevacuum chamber in relation to the contact portion and has a componentmounting surface for mounting the electrical component. The controlmodule is configured to cause relative movement between the support andthe load sensor so that a contact surface of the electrical component isbrought into close proximity with the contact portion. When the contactportion has solder thereon and the solder is brought into contact withthe contact surface, the load sensor measures force arising from wettingof the solder to the contact surface. The memory stores computer programinstructions which, when executed by the computer processor, cause thecomputer processor to control operation of the load sensor and thecontrol module.

Yet another aspect relates to computer readable storage storing computerprogram instructions which, when executed by a computer system, causethe computer system to control an apparatus comprising a vacuum chamberand a load sensor, the load sensor having a contact portion disposedwithin the vacuum chamber. Execution of the stored computer programinstructions by the computer system causes the computer system tocontrol the apparatus to: apply flux to the contact portion; create avacuum in the vacuum chamber; apply solder to the contact portion; causerelative movement between an electrical component and the contactportion so that the electrical component is brought into close proximitywith the contact portion and the solder contacts a contact surface ofthe electrical component; and measure by the load sensor force arisingfrom wetting of the solder during contact with the contact surface.

Referring now to FIG. 1, there is shown a schematic front view of anexample testing apparatus 100 for testing the solderability ofelectrical components 140, such as SMT components, by measuring wettingforces (i.e. surface tension) during contact of solder to the electricalcomponents 140. The schematic of the apparatus shown in FIG. 1 is not toscale and is provided for purposes of illustration only.

The testing apparatus 100 has a vacuum chamber 110 with a load sensor120 mounted thereon and a support module platform 130 contained withinthe vacuum chamber 110. One or more electrical components 140 aremounted to, or otherwise held on, a heating element 144 that is situatedon the platform 130. Also situated on platform 130 are a fluxreceptacle, such as flux container 150, and a solder receptacle, such assolder container 152. The vacuum chamber 110 also has an imaging device170, such as a camera, directed to capture images during testing. Theimages can be viewed by the test supervisor to make positioningadjustments during testing, if necessary.

Vacuum chamber 110 is preferably formed as a cabinet and has an opening(not shown), such as a door, for receiving the electrical components andconsumable materials, such as flux and solder. This opening must beclosable and sealable so as to be air tight, but otherwise may take anysuitable shape or form. Vacuum chamber 110 is supported by a vibrationtable 134 that is suitable for maintaining the vacuum chamber 110motionless despite external vibrations or movements that would otherwisebe transmitted through the structure supporting the vacuum chamber 110.Thus, the vibration table 134 prevents transmission of any such externalvibrations or movements to the platform 130 and other parts in thevacuum chamber 110, thereby providing greater reliability of testresults. The vibration table 134 may include a pneumatic vibrationisolation system such as is commercially available.

Vacuum chamber 110 also comprises an outlet 112 through which air andother gases are withdrawn from the vacuum chamber 110 (when sealed). Avacuum pump 114 or other vacuum generating device is used todepressurize the internal volume of vacuum chamber 110 and thus create avacuum therein. Vacuum chamber 110 is suitably sealed againstinadvertent depressurization. Vacuum pump 114 may be a suitablecommercially available roughing pump or roughing/diffusion pump system,for example. Vacuum pump 114 preferably has a pressure sensor associatedtherewith and a suitable input/output interface for external computercontrol of the vacuum pump 114. Alternatively, the vacuum pump may notinterface with an external control device and may be manually operatedby the test supervisor.

Moveable support platform 130 is positioned within vacuum chamber 110and is movable inside the vacuum chamber 110 in three dimensions, alongX, Y and Z axes. The movement of platform 130 is bounded by the confinesof vacuum chamber 110 and is controlled by servo motors (not shown) inplatform 130 that are driven by control signals received via controlcable 132. Platform 130 may be any suitable commercially available XYZstage with high resolution positioning in at least the vertical axis.Such resolution is at least of micrometer precision.

Flux container 150 may be supported directly by platform 130 or by asupport member interposed between the flux container 150 and platform130. Flux container 150 is preferably formed of steel and has acloseable opening at the top for allowing tip portion 128 of load sensor120 to be dipped into flux contained in flux container 150. Thecloseable opening of the flux container 150 is preferably biased towardsa closed position, for example by spring loading. Preferably, theclosable opening is automatically opened by some form of mechanicalactuation when tip portion 128 is positioned above flux container 150and is brought within a predetermined vertical distance of the opening.

Solder container 152 is preferably positioned on a heating plate 154,which is situated on platform 130. Heating plate 154 preferably has aresistive heating element therein and is thermally insulated fromplatform 130. Alternatively, instead of heating element 154 being formedas a plate, it may be formed as a coil around the outside of soldercontainer 152 or it may use an alternative heat source.

In order to sense the temperature of the solder in solder container 152,a temperature sensor 162, as such as a thermocouple, is positioned totake temperature measurements corresponding to the temperature of thesolder in solder container 152. Instead of a thermocouple, thetemperature can be measured using a thermal camera. Like flux container150, solder container 152 has a closeable opening at its top which isbiased towards a closed position but which is openable for dipping tipportion 128 into the solder. The closeable opening of solder container152 is preferably opened automatically by a form of mechanical actuationwhen tip portion 128 is positioned above solder container 152 andapproaches within a predetermined vertical distance of the opening.Solder container 152 preferably also has an automatic or mechanicallyactuable wiper 156 for removing dross from the top of the molten solder.The solder container 152 is preferably formed of tungsten. The heatingplate may be formed of a suitable material for resistance heating, suchas an iron-nickel-chromium alloy, a nickel-chromium alloy, Inconel™ orKanthal™.

Heating element 144 may be of any suitable commercially available typehaving a relatively small surface area (but relatively large compared tothe electronic components) and with good spatial temperature control soas to provide even heating across the surface that supports theelectrical components. Heating element 144 may have a temperaturesensing device 160, such as a thermocouple, integrally formed therein orseparately formed but appropriately positioned so as to sense atemperature of the upper surface of heating element 144 to which theelectrical components 140 are secured or mounted. Temperature sensingdevice 160 may alternatively employ a thermal imaging camera.

Each electrical component 140 is secured to the top surface of heatingelement 144. This surface may be used as the mounting surface formounting only a single electronic component 140 or it may be used tomount a number of electronic components 140 in series, for example inthe order of ten or so. Each electronic component 140 is secured to themounting surface of heating element 144 by a mounting member 142, whichmay be in the form of a clip, arm, bracket or other mechanical means forsecuring the electrical component 140 against inadvertent movement onthe mounting surface during the testing. Alternatively, other means maybe used to secure the electrical components 140 to the mounting surface,such as suction, adhesion or magnetic attraction.

Load sensor 120 is of a suitable commercially available type havingmicroNewton measurement accuracy, such as an atomic force microscope(AFM), for example. Load sensor 120 is positioned on top of the vacuumchamber 110 so as to reside partly outside of the vacuum chamber 110 andpartially within the vacuum chamber 110. Load sensor 120 has adownwardly projecting pin 124 that is disposed mostly within the vacuumchamber 110 but is connected to a measurement and control portion 125that is positioned outside of the vacuum chamber 110. Pin 124 is used tomeasure the wetting forces during testing. The forces exerted on pin 124are sensed by known elements within the measurement and control portion125. Load sensor 120 communicates with an external computer system 210(shown in FIG. 2 and described in further detail below) via a suitablecommunications cable 122. In an alternative embodiment, load sensor 120may be located entirely with vacuum chamber 110.

Pin 124 is preferably formed of a material that is non-conductiveelectrically and thermally. Pin 124 is preferably formed of alumina.Alternatively, pin 124 may be formed of a silicon carbide, siliconnitride or zirconia. Pin 124 may be approximately cylindrical or mayhave an alternative elongate shape with a small thickness or diameter.The diameter of pin 124 may be about 0.5 mm, for example.

Pin 124 may have a cooling coil 126 disposed along a portion of pin 124proximally of contact tip portion 128. Pin 124 preferably also has athird heating element 180 for resistive heating of tip portion 128.Because tip portion 128 needs to be heated to a relatively hightemperature by heating element 180, cooling element 126 is used toreduce heat conduction to the measurement and control portion 125 ofload sensor 120.

Tip portion 128 is preferably formed of iron. The heating element 180may be formed of an iron nickel chromium alloy. Alternatively theresistance heating element 180 may be formed of a nickel chromium alloy,Inconel™ or Kanthal™. The downwardly facing surface of tip portion 128is that which is fluxed and dipped in solder container 152 and is of asufficient dimension to retain a small but appropriately sized andcohesive globule of solder thereon through surface tension, despite thepull of gravity.

A temperature sensor 164 is positioned toward the end of pin 124,adjacent to portion 128 and distal (i.e. toward the tip) of coolingelement 126. Temperature sensor 164 is positioned to sense thetemperature of tip portion 128. For this purpose, a thermocouple may beused or, alternatively, a thermal imaging camera may be used. Thetemperature sensors 160, 162 and 164 shown in FIG. 1 are thermocouplesand are preferably of type T or K with a linear response in the 0 to300° Celsius range. If thermal imaging cameras are used, these will notbe positioned as indicated by the reference indicators in FIG. 1 ortemperature sensors 160, 162 and 164, but will instead be positionedaway from, but directed toward, the location at which it is desired tosense the temperature. Such thermal imaging cameras may be mounted on aninterior wall of the vacuum chamber, for example, and trained on theirrespective points of interest.

Referring also to FIG. 2, there is shown a system 200 for testing thesolderability of electrical components 140. System 200 includes theapparatus 100 and a computer system 210 for controlling the apparatus100 to perform the solderability testing. System 200 further comprises acontrol and communication module 250 for enabling computer system 210 toprovide control signals to components within apparatus 100 and toreceive output signals from those components where appropriate. Controland communication module 250 also performs analog-to-digital anddigital-to-analog conversion functions, where appropriate. System 200further comprises a cooling water supply 260 and a heating controlmodule or circuit 270. Cooling water supply 260 provides cooling waterto cooling element 126 in load sensor 120 and heating control module 270controls power to heating elements 144, 154 and 180.

Computer system 210 comprises a user interface 220 to allow a supervisorof the solderability testing to configure and initiate the testingprocedure. Computer system 210 also comprises a processor 230 incommunication with the user interface 220 and a memory 240 accessible toprocessor 230. Memory 240 stores computer program instructions whichmake up software modules used by system 200 during the solderabilitytesting procedure. Such software modules include, for example, aplatform control module 242, a load measurement module 244, atemperature measurement module 246 and a heating and cooling controlmodule 248. Processor 230 accesses the computer program instructions ofeach of the software modules in memory 240 and executes the instructionsas appropriate, including, for example, transmitting controlinstructions to control and communication module 250 to operate thevarious elements within apparatus 100.

Sensed conditions within apparatus 100, for example such as the internalpressure of the vacuum chamber 110, the platform position, the sensedtemperatures, and optionally the images being received at camera 170,are monitored by processor 230 via control and communication module 250.Such sensed conditions are used by the software modules to ensure thatthe testing procedure is being carried out according to preconfiguredtesting parameters. The output of camera 170 may be provided directly toa display independent of computer system 210 or it may be provided to asuitable image processor within computer system 210 for display via userinterface 220.

User interface 220 may include any suitable interface means, such as adisplay, keyboard and mouse. One or more of the software modules storedin memory 240 may include existing software applications, for examplesuch as those which may be provided with the purchase of elements inapparatus 100. For example, load sensor 120 may have appropriatesoftware that is commercially available with purchase of load sensor 120and which may constitute the load measurement module 244. Additionally,platform control module 242 may comprise software provided by the makerof platform 130 and specifically tailored for control of platform 130.Other of the software modules stored in memory 240 may include routinesdeveloped in an appropriate commercially available software applicationfor control and measurement purposes, such as LabVIEW™ available fromNational Instruments.

Referring now to FIG. 3, a method 300 of testing the solderability ofelectrical components is described in further detail. Method 300 beginsat step 305 with a set up procedure. In the set up procedure, the vacuumchamber 110 is not sealed and its opening may be open. During the set upprocedure, the flux container 150 is filled with flux if required andthe solder container 152 is filled with a suitable volume of solidsolder, if required. One or more electrical components 140 arepositioned on the mounting surface of heating element 144 and theelectrical components 140 are fixed in place using the mounting members142 or alternative means of securement. When the electrical components140 are secured on the mounting surface, they are placed so as to havetheir test surfaces in a horizontal position and face up. The mountingmembers 142 should be positioned so as not to obstruct contact betweenthe testing surfaces of the electrical components 140 and the contacttip portion 128 during testing.

Set up step 305 may also include verifying the operational status ofeach of the components of apparatus 100. For example, the operability ofvacuum pump 114 may be checked, along with the operational status of theother sensing and control elements in apparatus 100, such as platform130, camera 170, load sensor 120, the heating elements 144, 154 and 180and the temperature sensors 160, 162 and 164.

Once the set up procedure is complete, the opening of vacuum chamber 110is closed and flux is applied to pin 124, at step 310. In order to applyflux to pin 124, platform 130 is moved according to control signalsreceived through cable 132 so as to position flux container 150 beneathtip portion 128 and platform 130 is then slowly raised so as to dip tipportion 128 into flux container 150 and immerse it in flux. Tip portion128 is then withdrawn from flux container 150 by lowering platform 130and the opening of flux container 150 is closed in order to preventevaporation of the flux. Preferably, about 2.5 mm of the pin 124 islowered into the flux container 150.

At step 315, vacuum chamber 110 is sealed and evacuated through outlet112 by vacuum pump 114. Vacuum pump 114 depressurizes the vacuum chamber110 so as to reduce the pressure within vacuum chamber 110 to apredetermined pressure level of about 0.01 torr, for example. Thepressure inside vacuum chamber 110 should be low enough that thermalconduction currents are negligible, but the higher the pressure that canbe tolerated, the better. The higher the pressure that can be tolerated,the fewer practical difficulties are encountered with maintaining thevacuum conditions.

At step 320, following evacuation of vacuum chamber 110, soldercontainer 152 is heated by heating element 154 to ensure that the soldertherein is in a molten state. If necessary, wiper 156 is used to wipethe dross from the top of the molten solder once it has melted. Whilethe solder is melted, heating elements 144 and 180 are used to heat theelectrical components 140 and tip portion 128, respectively.

Once the solder, the electrical components 140 and the tip portion 128are all heated to the desired degree, as sensed by respectivetemperature sensors 162, 160 and 164, solder is applied to tip portion128 of pin 124. The electrical components 140 should be heated to about100 degrees Celsius, while the solder and tip portion 128 should beheated to temperatures above the melting point of the solder, which mayvary according to the type of solder.

Application of solder to tip portion 128 is done by moving platform 130so as to position solder container 152 beneath tip portion 128 and thenraising platform 130 so as to immerse tip portion 128 in soldercontainer 152 by about 2.5 mm. During or prior to solder container 152being raised towards tip portion 128, its top opening is opened and,once tip portion 128 is withdrawn, the opening is again closed. Oncesolder has been applied to the tip portion 128 and platform 130 has beenlowered to withdraw tip portion 128 from solder container 152, camera170 may be used to visually verify that an appropriate amount of solderis suspended from tip portion 128. Signals from load sensor 120 may alsobe used to verify that an appropriate amount of solder is suspended fromtip portion 128.

At step 330, platform 130 is again moved relative to pin 124 so as tobring a testing surface of electrical component 140 into contact withthe globule of solder suspended from tip portion 128. This contact isachieved slowly and with great precision. Once load sensor 120 detectsthe exertion of a wetting force brought about by contact of the solderon tip portion 128 with a test surface of electrical component 140, asignal is sent by load sensor 120 to processor 230 via cable 122 andprocessor 230 then instructs platform 130 (via cable 132) to ceasemovement. The load sensor may wait until it detects force above apredetermined threshold before causing the platform 130 to stop.

Once platform 130 has stopped moving electrical component 140 towardstip portion 128, load sensor 120 measures the forces exerted on pin 124by surface tension resulting from the wetting of the solder to the testsurface of electrical component 140. The wetting forces are measured fora predetermined period of time, for example such as 5 to 20 seconds oruntil the forces reach an equilibrium, depending on the sample beingtested, and the measurements are uploaded from load sensor 120 toprocessor 230 in real time and recorded by processor 230 in memory 240.Contact of the solder on pin 124 with the electrical component should bemade in such a way as to avoid the solder sliding off tip portion 128.Otherwise, the value of the test data will be minimal.

At step 340, processor 230 may determine that, according to thepreconfigured testing procedure, there are further electrical components140 on the mounting surface that remain to be tested or the sameelectrical component 140 has a further surface to be tested.Alternatively, this determination may be made by the test supervisor.Either way, steps 325 to 335 are repeated for each such furtherelectrical component 140 or surface. Once testing has been performed onall electrical components 140 on the mounting surface and all componentsurfaces, processor 230 analyzes the measured test data and generatesone or more reports, at step 345, for presentation to the testsupervisor. Such reports may include, for example, plots of the buoyancyand wetting forces as a function of time and a summary of the testconditions.

While method 300 is preferably performed in the order of the stepsdescribed above, alternative embodiments may reverse the order of someof the steps. For example, the order of steps 315 and 320 may bereversed.

It should be understood that a reference herein to a test surface of anelectrical component includes conductive pads and other forms ofelectrical terminations or leads. Further, while reference is madeherein to SMT components as one form of electrical component, it shouldbe understood that other kinds of electrical components that rely onsolder to form electrical connections on current boards may be thesubject of testing using the described embodiments.

1. A method for use in determining solderability of an electricalcomponent, the method comprising the following acts in the orderpresented: mounting at least one electrical component to a componentmounting surface within a vacuum chamber; applying flux to a contactportion of a load sensor, the contact portion being disposed within thevacuum chamber; creating a vacuum in the vacuum chamber; applying solderto the contact portion; causing relative movement between the at leastone electrical component and the contact portion so that a respectiveelectrical component is brought into close proximity with the contactportion and the solder contacts a contact surface of the respectiveelectrical component; and measuring by the load sensor force arisingfrom wetting of the solder during contact with the contact surface. 2.The method of claim 1, wherein the at least one electrical componentcomprises at least two electrical components and the method furthercomprises, for each electrical component, the applying flux to thecontact portion, the applying solder to the contact portion, the causingrelative movement and the measuring by the load sensor.
 3. The method ofclaim 1, wherein the at least one electrical component is disposed belowthe contact portion and wherein the causing relative movement furthercomprises moving the at least one electrical component relative to thecontact surface while the contact surface is held stationary.
 4. Themethod of claim 1, wherein the applying flux to the contact portionfurther comprises moving a flux container containing flux relative tothe contact portion to dip the contact portion into the flux container.5. The method of claim 4, wherein the contact portion of the load sensoris dipped into the flux container to a depth of about 2.5 mm.
 6. Themethod of claim 1, wherein the applying solder to the contact portionfurther comprises moving a solder container containing solder relativeto the contact portion to dip the contact portion into the soldercontainer.
 7. The method of claim 6, wherein the applying solder to thecontact portion further comprises heating the solder container to turnthe solder contained therein in a molten state.
 8. The method of claim6, wherein the applying solder to the contact portion further comprisesheating the electrical component.
 9. The method of claim 6, wherein theapplying solder to the contact portion further comprises heating thecontact portion of the load sensor to a temperature above the meltingpoint of the solder.
 10. The method of claim 6, wherein the contactportion of the load sensor is dipped into the solder container to adepth of about 2.5 mm.
 11. The method of claim 1, wherein the creating avacuum further comprises reducing the pressure in the vacuum chamber toabout 0.01 torr.
 12. The method of claim 1, wherein each at least oneelectrical component has a plurality of contact surfaces and the methodfurther comprises, for each contact surface, the applying flux to thecontact portion, the applying solder to the contact portion, the causingrelative movement and the measuring by the load sensor.
 13. The methodof claim 1, wherein the mounting at least one electrical componentfurther comprises fixing the at least one electrical component to thecomponent mounting surface using a mounting member.
 14. The method ofclaim 1, wherein the at least one electrical component are mounted tothe component mounting surface so that the contact surface is upwardlyfacing.
 15. The method of claim 14, wherein the contact portion of theload sensor is downwardly facing.
 16. The method of claim 1, furthercomprising ceasing relative movement between the at least one electricalcomponent and the contact portion when the load sensor measures theforce arising from wetting of the solder.
 17. The method of claim 16,further comprising ceasing the relative movement between the at leastone electrical component and the contact portion when the load sensormeasures force above a predetermined threshold.
 18. The method of claim1, wherein the measuring by the load sensor further comprises measuringthe force arising from wetting of the solder for a predetermined periodof time.
 19. The method of claim 18, wherein the predetermined period oftime is between 5 and 20 seconds.
 20. The method of claim 1, wherein themeasuring by the load sensor further comprises measuring the forcearising from wetting of the solder until the force reaches equilibrium.